Browsing by Subject "Pimephales promelas"

Now showing 1 - 5 of 5
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    Conditioned Alarm Behavior in Fathead Minnows (Pimephales promelas) and Test Their Ability of Differentiate Between Different Visual Stimulus (i.e. Red Light, Green Light and Blue Light)
    (2012-04-11) Al-Shamisi, Meera
    Fathead minnows (Pimephales promelas) were tested for their ability to associate predation risk with novel visual stimuli after visual stimulus was presented simultaneously with chemical alarm cues. Minnows gave a fright response when exposed to skin extract (chemical alarm cue) and an artificial visual light stimulus. When they were retested with light stimulus alone, the minnows that had previously been conditioned with alarm cues and light exhibited anti-predator behavior in response to the visual cue. To carry out this experiment, we hypothesized that fathead minnows would learn to associate predator risk stimulus with visual stimulus, and they would be capable to differentiate between the three different colors by showing associate response to the red color and no response to the green and blue lights. The results of this experiment have far-reaching implications because they provide important information on the role of visual stimuli in the ecological environment of fishes.
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    Effects of nanosilver on Daphnia magna and pimephales promelas.
    (2010-08) Hoheisel, Sarah M.
    The increasing use of nanosilver in consumer products and the likelihood of environmental exposure warrant investigation into the toxicity of nanosilver to aquatic organisms. A series of studies were conducted comparing the potency of nanosilver to ionic silver (Ag+) at acute and sublethal levels. The results of these tests were examined for evidence that nanosilver acts by a different mechanism of toxicity than Ag+, with the goal of estimating the adequacy of current water quality regulations based on the toxicity of Ag+ to protect against environmental effects of nanosilver. A variety of simple methods to separate Ag+ from nanosilver by physical exclusion or charge selectivity were assessed in preliminary studies for the ability to provide insight into the mechanism of nanosilver toxicity. In a definitive study, ion exchange resin was used to remove Ag+ from nanosilver (confirmed by the complete removal of silver from AgNO3 solutions) in order to determine the importance of Ag+ to acute toxicity of nanosilver to Daphnia magna. The acute toxicity of nanosilver to D. magna after ion exchange was shown to be similar to that of untreated nanosilver, suggesting that Ag+ did not contribute significantly to the toxicity of the suspensions, or that ion release occurred rapidly after ion exchange. D. magna juveniles were exposed to four sizes of nanosilver (10, 20, 30 and 50 nm) and Ag+ and 48-h LC50s were calculated for each material. Based on mass concentrations, all nanosilver sizes were less acutely toxic than Ag+, and a trend of increasing toxicity with decreasing average diameter of nanosilver was observed, with LC50s ranging from 19-42 times higher than that of Ag+. Calculations of nanosilver specific surface area and theoretical surface atoms revealed little to no difference in LC50s among the four sizes, suggesting that toxicity may be dependent on the surface properties of nanosilver. Equivalent calculations for an ionic Ag exposure series resulted in the finding that, in terms of total surface Ag atoms, all sizes of nanosilver were more acutely toxic than equivalent exposures of pure Ag+. This implies either that a second mechanism of toxicity exists for nanosilver which increases its overall potency, or that the calculation of surface atoms was an underestimate due to the continuous release of Ag+ from nanosilver into the matrix. Acute-to-chronic ratios (ACRs) were obtained for Pimephales promelas (<24 hours post hatch) exposed to both Ag+ and nanosilver, to test the hypothesis that a difference in these ratios would indicate different mechanisms of toxicity. The results of 96-h acute and 7-day sublethal toxicity tests produced ACRs for Ag+ and nanosilver that were not significantly different based on their overlapping confidence intervals. Furthermore, the observation that the nanosilver ACR was smaller than that of Ag+, suggest that if there is a separate toxicity mechanism in nanosilver, it is unlikely to result in environmental effects beyond those that would be expected from an Ag+ exposure. Further studies are needed to determine the degree to which the results of the ion exchange and size-dependent toxicity tests can be attributed to nanosilver dissolution. Overall, the results of these tests do not provide unambiguous evidence for a mechanism of nanosilver toxicity other than Ag+. The U.S. EPA maximum allowable silver concentration for natural waters is based on dissolved silver, defined as that which passes through a 0.45 μm filter, which is considerably larger than the average size of nanosilver aggregates in the exposure media. Therefore, the presence of nanosilver in the environment will increase the apparent dissolved Ag concentration, resulting in increased protectiveness of this criterion.
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    Habitat complexity and shoaling behavior in Pimephales promelas
    (2011-02-01) Gahr, Carolyn
    Hamilton’s selfish herd theory dictates that individuals will seek protection from predation by locating to the center of a group in order to hide behind other members. This study focused on applying the selfish herd theory to shoaling behavior between habitats of varying complexity. Fathead minnows were placed either in a simple or complex environment and shoaling behavior was measured in response to the presence or absence of a predator. The results indicated that habitat complexity and predator presence/absence did not have a significant effect on shoaling behavior. While the data were not significant the results did suggest that in complex environments shoaling behavior is independent of predation risk, which indicates individuals are seeking shelter similar to Hamilton’s selfish herd theory.
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    Predation Risk and Habitat Complexity: Shoaling Behavioral Changes in Pimephales Promelas
    (2011-02-01) Brass, Steven
    Grouping behavior in fish is a well‐understood phenomenon present in numerous species. Habitat and predation risk are two major influences on this behavior and our experiment was designed to quantify the how shoaling behavior in Pimephales promelas differed with an increase in complexity of environment and predation risk. We found that shoaling behavior was not different when habitat complexity increased or in the presence of a natural predator (Perca flavescens). While both of these factors are expected to affect grouping behaviors we were unable to quantitatively see a difference in the distances between individuals and the shoal diameter.
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    Time Place Learning in Fathead Minnows, Pimephales promelas
    (2013-03-19) Hill, Alicia; Aiken, Stephanie
    Previous studies have shown that some animals can exhibit time-place learning. Our study focused on the ability of time-place learning in fathead minnows. To test this we placed groups of 8 minnows into 11 tank replicates. To prevent room position bias, some tanks had food placed on the right side in the morning and on the left side at night. Remaining tanks had food placed vice versa. After one week of feeding, we recorded the total average positions of minnows in comparison to the correct side where they should have been in the morning and night. Our results showed no significant differences in the total average positioning of minnows within the tanks (t=-1.247, df=10, P=0.241). In our study we found that fathead minnows did not exhibit time-place learning. Future studies could replicate our experiment and change the length of observation time or number of minnows in a tank to further test for time-place learning.